This invention relates to devices for movement along passages.
Devices are generally known applicable in use for movement along passages, e.g. passages which require examination or certain treatments. In particular, devices are made which are intended for use in medical procedures, i.e., when the devices are for movement along passages of humans and animals. In this latter regard, such devices may include, for instance, a sound, a colonoscope, catheter or endoscope.
It is generally accepted that the use of any device of the above or similar medical type upon their persons, is not welcomed by patients who, while accepting that the use of such devices is necessary, face their usage with physical and emotional repulsion. Feelings of humiliation and personal degradation may also occur, particularly during the use of a colonoscope. These feelings and fears, together with the fear of diagnosis, can cause great tension and resulting spasm, which could contribute to problems during the procedure, and possibly cause pain.
However, of primary importance during the use of a colonoscope is the avoidance of injury to the patient and the completion of procedures in a safe and speedy manner, and in a predictable time. With this in mind, and in order to alleviate the above problems, many colonoscope procedures are performed under a light anaesthetic which includes an amnesiac component. This results firstly in the patient being able to report pain during the procedure, when he feels it, while ideally not feeling the pain sensations afterwards. Secondly, it warns medical staff of impending difficulties.
Many colonoscopic procedures are routinely performed without undue difficulty at present, but a certain percentage are complicated and cannot be completed with known devices. In addition, known devices may present problems in successfully negotiating twists and turns in a colon. This adds to an inordinately lengthy average procedure time, which adds to the stress of both the patient and the attendant medical staff. The lengthy procedure time results, on average, in colonoscope procedures being undesirably expensive, whether or not they are successfully completed.
In attempts to mitigate all of the above fears, various types of constructions of device have been used and suggested. In one basic type of construction of device, a flexible sheath for covering an elongate diagnostic or surgical tool is provided on its outer surface with inflatable devices sequentially positioned along the sheath. These inflatable devices, sometimes with elastic means extending between them, are inflated and deflated in predetermined order to effect movement of the sheath along the passage. Such movement is slow and intermittent and, it is believed, the continual inflation and deflation of the inflatable devices into and out of contact with the colon wall, must add to patient discomfort. Examples of this type of device are described in U.S. Pat. Nos. 4,148,307 and 4,676,228. In another basic type of construction, an elongate sheath is everted during inflation to urge a tool contained within the sheath along the passage. With this type of construction, in order to evert the sheath, the sheath must have a radially outer region inflated into contact with the passage wall, and a radially inner region which contacts the surface of the tool. However, a problem which is inherent in use of this construction is that the radially inner region of the sheath must move relative to, and upon, the surface of the tool during the eversion procedure in feeding the tool along the passage. This relative movement produces frictional resistance to movement of the device along a passage, e.g. a colon, which adds difficulty to exploratory or surgical procedures. Frictional resistance is exacerbated by inflation pressure forcing the radially inner region against the tool surface. This produces severe problems concerning freedom of movement of the device, particularly around turns and restrictions of the colon. Prior U.S. Pat. No. 5,259,364 acknowledges that the radially inner region of an eversible tube travels at twice the speed of an endoscope to move the endoscope along a colon passage. In the disclosure, it is stated that to obtain substantially no frictional forces between the tube and endoscope, fluid under pressure is directed between the radially inner region of the tube and the endoscope to space them apart.
The present invention seeks to provide a device for movement along a passage which lessens the above problems in use. When used for medical purposes, the device of the invention seeks to avoid injury to the patient while enabling completion of procedures in a safe and speedy manner and in a predictable time.
According to one aspect of the invention, there is provided a device for movement along a passage comprising:
elongate tool having a major axis, distal and proximal end regions, and a sheath abutment element at the distal end region of the tool;
an elongate inflatable sheath surrounding the tool, the sheath having an annular inflatable region disposed between the abutment element and the proximal end region of the tool, and an annular extension region for the annular inflatable region, the annular extension region having a plurality of sequentially interconnected sheath parts extending from the inflatable region, the sheath parts being relatively oriented to face each other to locate the annular extension region around the distal end region of the tool with the annular extension region movable forwardly together with the distal end region of the tool;
an annular inflation chamber defined between the inflatable region and the outer surface of the tool; and
means for introducing pressurized fluid into the chamber to inflate the inflatable region of the sheath, when inside the passage, and to cause inflationary pressure then to act against the sheath abutment element to move the tool forwardly along the passage accompanied by sequential reorientation of the sheath parts and their sequential movement into, and lengthen, the inflatable region.
When the device of the invention defined above is to be used within passages provided by inanimate matter, these passages would normally be expected to be provided with a rigid wall, e.g. in the case of metal or plastic pipes. In such a case, the radially outwards expansion of the inflatable region of the sheath would be constrained by the rigid wall and the sheath would have to expand axially, upon continued introduction of the pressurized fluid, so that the tool was moved along the passage. Where, however, the device is to be used upon living beings, particularly humans, then the sheath should have limited radial expansion, i.e., to a desired maximum. The sheath may be formed from an inelastic material, such as an inelastic polymer, e.g. polyurethane film. Alternatively, the sheath may include a plurality of longitudinally inextensible fibers which are oriented in at least one particular direction for the purpose of limiting radial expansion. Hence, the sheath should be designed so as not to apply undue pressure to the wall of the passage, e.g. a colon, but may apply sufficient pressure either merely to engage the passage wall or with a small acceptable radial enlargement of the passage. Thus the sheath will grip the passage wall and then expand progressively along its length while, simultaneously, the tool, e.g. a colonoscope, is moved forwardly by the inflationary pressure. When the device is used for medical purposes, the limit to radial expansion of the sheath thus may help to lessen any discomfort and anxiety of a patient. Sudden increases and decreases of inflationary pressure at localized regions of the passage are avoided, such as must be provided by devices having inflatable bags inflated and deflated in specified order to move a tool incrementally along the passage.
In addition to the above, and to render the device of the invention more easily useable in medical situations, and therefore to make use of the device more acceptable to a patient, ease of movement of the tool along the passage is maximized. This is because frictional resistance to movement between relatively moveable parts of the device is minimized. Hence, when required, such as for colonoscope use, movement along curved tortuous regions of the colon is made easier, thereby increasing chances of full traverse to the caecum. Minimization of the frictional resistance is effected by having the inflation chamber defined partly by the tool outer surface so that the sheath does not have a radially inner portion which must slide upon the tool surface and which would create frictional resistance.
In contrast to having a radially inner portion of sheath sliding upon the tool surface, a structure of the above invention has, instead, the annular extension region which moves forwardly along the passage together with and at the same rate as the tool. The sheath parts of the extension region are deployed from the distal end of the tool.
In one arrangement, the annular extension region is connected to the inflatable region by a distal end fold of the sheath. The distal end fold preferably engages the sheath abutment element and under inflation pressure, the sheath everses by the distal end fold rolling forwardly under inflation forces acting against the abutment element thereby urging the tool forwardly. The annular extension region progressively moves through the distal end fold, as it rolls forwardly, to progressively become part of the axially lengthening inflatable region of the sheath. The annular extension region in this arrangement, may be supported radially inwards upon the tool, and may be contained within a cylindrical housing secured around the tool.
In another arrangement, the sheath has a minimum radius of collapse whereby the annular extension region is disposed at a larger diameter than a region of the tool which is located radially within the extension region. In this case, means is required to maintain the extension region spaced by an annular gap from that region of the tool. It is convenient if this spacing-maintaining means comprises an axially extending part of the abutment element and which is itself spaced from the above region of the tool. In a practical structure, this part of the abutment element contains and supports the extension region to restrain it from radial outward expansion under inflation pressure, and until each sheath part of the extension region moves into and becomes part of the inflatable region of the sheath as forward movement proceeds. In this practical structure, the extension region is thus located forwardly of the inflatable region of the sheath with a radially extending interconnecting sheath portion located intermediate the inflatable region and the extension region. During inflation, the sheath parts move sequentially radially outwardly into the inflatable region. With this structure, inflation pressure acts, not only to inflate the inflatable region, but also directly through an annular gap between the extension region of the sheath and the tool to be applied directly against the abutment element to move the tool forwardly. Thus, inflation forces do not act against the abutment element through the intermediary of a distal end fold as in the arrangement of the invention previously discussed. Hence, creation of any friction forces which may be caused by sliding of such a fold against the abutment element during sheath eversion is avoided.
The annular extension region may have its sheath parts provided by a plurality of sequentially interconnected annular folded portions positioned around the distal end region of the tool. The folded portions are caused to sequentially unfold as inflationary pressure acts against the sheath abutment element so as to move the folded portions into and progressively lengthen the inflated inflatable region. Alternatively, the annular extension region is crumpled to form the sheath parts. Crumpling is progressively removed as inflationary pressure acts against the sheath abutment element to move the sheath parts into the inflated inflatable region. In a case where the extension region is provided by annular folded portions, these are preferably positioned radially outside of, and are superimposed upon, one another. In the above arrangement employing a distal end fold and where the extension region has annular folded portions superposed upon one another, it is preferable for the folded portions to unfold sequentially, during eversion, radially inwardly from the radially outermost folded region. Hence, no slippage of the sheath upon the tool occurs during unfolding and unnecessary frictional resistance to movement of the tool is avoided.
According to a further aspect of the invention, there is provided a device for movement along a passage comprising:
an elongate tool having a major axis, distal and proximal end regions, and an inflatable sheath abutment element at the distal end region of the tool;
an elongate inflatable sheath surrounding the tool, the sheath having an annular inflatable region disposed between the abutment element and the proximal end region of the tool and an annular extension region interconnected with the annular inflatable region;
an annular inflation chamber defined within the annular inflatable region of the sheath; and
means for introducing pressurized fluid both into the chamber to inflate the inflatable region of the sheath and the sheath abutment element, when inside the passage, and, with the abutment element inflated, to cause inflationary pressure to act against the sheath abutment element to draw the tool forwardly along the passage accompanied by progressive movement of the annular extension region of the sheath into the inflated region so as to increase the length of the inflated inflatable region.
The sheath and the abutment element are preferably both inflatable by limited amounts, which conveniently are to approximately equal outside diameters. Advantageously, after complete insertion of the device into the passage for whatever purpose, both the sheath and the abutment element may be deflated for easy removal. When the device is used in medical exploration and/or surgery, the ease of insertion and removal minimizes injury to the patient while adding to patient comfort and reduces possibility of pain and injury. In addition, the inflatable sheath abutment element is of a flexible nature and may deform somewhat according to change in shape of the passage. This provides a cushioning effect when contacting the wall of the passage, e.g. colon, so as to comply, at least to a degree, to the shape of the wall, thereby reducing resistance to forward movement along the passage while minimizing pain such as may be caused by colon distortion.